"It will take a decade or longer to collect data before the researchers can make clear the relationship between smog and people having a certain kind of disease," Fang Laiying, Beijing Municipal Commission of Health and Family Planning's director, said.

Sahba Maani, a Pulmonary and Intensive Care expert at Beijing United Family Hospital and Clinice, said, "There have been numerous studies showing that the risk of air pollution is even greater than we once thought."

He further noted a study published by the International Agency for Research on Cancer in 2013 that reviewed more than a thousand scientific studies from five various continents. The report revealed that "air pollution and particulate matter were both linked to lung cancer and should be classified as carcinogenic."

However, the BMCHFP's study does not conclude yet that long-term smog exposure could cause lung cancer.

Air pollution is a big problem in China that it is being dubbed as "airpocalypse." It has killed an estimated 1.6 million people in China every year, accounting for 17 percent of all deaths in the country.

"The intense rise in lung cancer [in China]... is ultimately related to smog," Dr. Zhao Xiaogang, deputy chief of thoracic surgery at the Shanghai Pulmonary Hospital of Tongji University, said. Zhao authored a poem that has gone viral across Chinese social media networks that acknowledges the link between smog and lung cancer.

Meanwhile, the commission, in cooperation with the Beijing Center for Diseases Control, issued a list of precautionary measures against smog. It advised people to stay indoors and wear face-tight masks, although masks are not advised to pregnant women and old people as this can cause breathing resistance.